**1. Introduction**

The X-ray astronomical satellite "ASTRO-H" was launched in February 2016 and carried hard and soft X-ray telescopes. However, an accident that occurred during adjustment caused the satellite to break up, and the project was canceled. For the launch of the successor by the Japan Aerospace Exploration Agency (JAXA) in 2020, an X-ray telescope needs to be rapidly fabricated at a lower cost than the ASTRO-H project. The X-ray astronomical satellite consists of over 1,200 super mirror pieces in a telescope with a diameter of 600 mm [1–3]. These mirrors are prepared using the "replica method" that presses and transcribes the mirror material on the surface into thin aluminum plates [4–7]. These techniques using precision molding dies [8–11] have also recently been applied not only for X-ray telescopes but also for various other optical components that require rapid and low-cost manufacturing.

Authors previously proposed the use of the "slumping method" as a thermo glass forming method to achieve rapid and low-cost manufacturing of optical components [12]. The slumping method can be used to manufacture next-generation X-ray telescope; in addition, it can be used for shape forming of glass super mirrors and other optical components. In our previous studies, a SUS304 stainless-steel molding die with nanoscale surface roughness was successfully prepared using the slumping method [13].

In this study, the precision polishing process for a SUS310S stainless-steel molding die as a heat-resisting metal was investigated using various polishing pressures, polishing times, and surface roughnesses. This technology was developed to manufacture super mirrors of space telescopes used in the field of aerospace. Therefore, the accuracy required for these products are so high levels such as "some nano meters or sub nanometers". By considering these results, it may be possible to open up new using fields of application with precision manufacturing and designing technology in the future.

### **2. Structure of X-ray telescope**

**Figure 1** shows a structure of the X-ray telescope structure [1]. The diameter of the X-ray telescope cylinder used in ASTRO-H is approximately 600 mm and consists of more than 1,200 super mirror pieces. The X-ray wavelength is below 1 nm, and the X-rays enter at an angle of less than 1° and are reflected twice by the interior surface of the mirror. The reflected X-rays are then focused on a detector positioned 8 m away. The super mirrors with a multi-layer film of "platinum carbon" used to reflect the X-rays by "Bragg reflection [1]"are approximately 0.2 mm thick and very smooth. The super mirrors are the main components of the X-ray telescope; however, their manufacture is difficult because of their arc-line shape and the highly precise surface roughness needed to enable detection of the X-rays. To meet these specifications, high-precision techniques are required to prepare the molding dies used to fabricate the super mirrors.

**Figure 1.** *Structure of the X-ray telescope structure [1].*

*Precision Polishing Techniques for Metal Molding Dies and Glass Forming Technology… DOI: http://dx.doi.org/10.5772/intechopen.99208*
